ON ENERGY OF RONTGEN AND BECQUEREL RAYS, ETC. 
57 
In one respect, however, some of {the radio-active substances, notably radium, differ 
in their type of radiation from X rays. Becquerel, Curie, and others, in a series of 
papers in the ‘ Comptes Rendiis,’ have shown that radium gives out a type of rays 
which are easily deflected by a magnet. This emission of rays similar in character to 
cathode rays of low velocity is very remarkable, Imt does not seem to lie a necessary 
accompaniment of a radio-active substance. For example, Giesel found polonium 
gave out rays deflected by a magnet, while Becquerel could obtain no magnetic 
action for the same substance. The rays which are deflected liy a magnet seem to he 
present or absent according to the mode of preparation of the substance, and depend 
possibly on the age of the specimens. Two impure and not very sensitive specimens of 
radium and polonium obtained from pitchblende have been tested by one of us, Init 
no magnetic action has been observed. Becquerel has found no trace of magnetic 
action in uranium radiation, and one of the authors has tested both uranium and 
thorium radiations in a magnetic field at atmospheric pressure and obtained negative 
results. 
The experiments of Curie and Becquerel have shown that, in radium, two types 
of rays are present, one of which is deflected by a magnetic field and the other is not. 
The non-deflected type is similar in character to secondary X rays, and the deflected 
ones similar to low velocity cathode rays. 
We thus see that the phenomena exhibited by the radio-active substances are not 
simple, and that they differ from one to the other. It is still possible, however, to 
form an approximate estimate of the energy of the radiation whatever its kind, 
provided the energy is all completely absorbed in ionizing the gas, and produces ions 
of the same kind. It seems probable that the radium rays acted on by a magnetic 
field are a type of cathode rays, and that they ionize the gas in their passage through 
it. The results of McLexxan^ clearly show that the energy of the cathode I'ays is 
lost in its passage through the gas, due partly to the work done in ionizing the gas in 
its path. Provided the ions produced by the deflected and undeflected rays of the 
radio-active substances are the same, and absorb the same amount of energy in their 
production, the relative energies of the radiations emitted can be compared by noting 
the total maximum current produced by the rays when completely absorbed between 
the electrodes. 
If n = the ratio of the currents between parallel plates for equal areas and 
thicknesses of the test substances and uranium oxide when the plates are at a 
sufficient distance apart to approximately absorb all the rays, then 
Energy radiated out by the test substances into the gas = n X the energy 
radiated by an equal area of uranium oxide. 
This will probably apply roughly to the conductivity produced by the deflected and 
undeflected rays. 
* ‘Roy. Soc. Pioc.,’ vol. 66, 1900; ‘Phil. Trans.,’A, vol. 195. 
VOL. CXCVL — A, 
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